The biomechanical capacity of the periosteum in intact long bones

Introduction The biological function of the periosteum is profusely described but its contribution to the biomechanical properties of the bone has been considered negligible. The purpose of this study was to examine the biomechanical properties of periosteum-preserved long bones. Materials and methods The biomechanical properties of both femora and tibiae of 30 male, 4-month-old Wistar rats were evaluated using a destructive three-point-bending testing protocol. In both bones from one side the periosteum was preserved, while in the contralateral bones the periosteum was stripped off. Ultimate strength, stiffness, energy absorption and deflection were derived automatically from the load-deformation curve recorded for each bone. Results As regards the femur, the periosteum-covered bones displayed statistically significant higher values for all parameters measured compared to the periosteum-stripped bones. Ultimate strength, stiffness, absorbed energy and deflection of stripped and periosteum-covered femora were, respectively, 146.76 +/- 44.71 and 196.01 +/- 41.47 N, 44.25 +/- 17.35 and 61.62 +/- 15.07 N/mm, 0.00054 +/- 0.00274 and 0.00011 +/- 0.00354 Nmm, 0.67 +/- 0.25 and 1.07 +/- 0.28 mm. In the tibia, only energy absorption (0.00353 +/- 0.00199 and 0.0010 +/- 0.00339 Nmm) and deflection (1.71 +/- 0.56 and 0.86 +/- 0.36 mm) were significantly higher in the periosteum-covered bones. The pattern of bone failure was also different in the two groups. In periosteum-covered bones the two bone parts remained in close apposition stabilized by the periosteal membrane, while in a few cases the periosteum was stretched or torn opposite the loading site. Conclusion The periosteum not only has significant biological function but also provides mechanical support to the bone and amplifies the biomechanical capacity of intact rat long bones in bending, probably taking advantage of its fibrous and elastic properties.